The present invention relates generally to occupant restraint devices for vehicles. In one aspect, it relates to an apparatus for tethering a vehicle seat, which is mounted on a suspension pedestal, against unwanted movement relative to the vehicle floor.
It is well known to mount a vehicle seat on a pedestal rather than securing it directly to the floor of the vehicle. Seat mounting pedestals may include mechanisms for adjustment of the static fore-aft position of the seat, and may also include mechanisms for adjustment of the static seat height. More sophisticated seat mounting pedestals are also known which include vertical and/or fore-aft suspension devices, for example springs, pneumatic cylinders, or air bags, which allow controlled movement (also known as xe2x80x9ctravelxe2x80x9d) of the seat with respect to the vehicle floor during operation of the vehicle. This seat travel tends to isolate the seat (and thus the occupant) from vibration and bouncing.
Most vehicles are now required to provide an occupant restraint system to reduce the likelihood of occupant injury during high acceleration events such as vehicle collisions or rollovers. According to Federal Motor Vehicle Safety Standard (FMVSS) testing, occupant injury is reduced when the forward and upward movement of the occupant is limited as much as possible. The limitation of the occupant""s overall movement is best accomplished by restraining the occupant against movement relative to the seat while simultaneously restraining the seat itself against forward and/or upward movement relative to the vehicle floor. Thus, the seat mounting system of a vehicle is often a component of the occupant restraint system.
In some applications, for example in the field of commercial vehicles and long-haul trucks, a wide variety of seats and suspension pedestals are produced by numerous manufacturers. Seats and pedestals are typically manufactured separately, rather than as a unit, so that a vehicle""s owner can select individual component according to his or her preferences. The selected components are then installed in the vehicle by the builder. The builder must ensure that the selected components are compatible in terms of both seat suspension operation and occupant restraint operation.
To accommodate the wide variety of seat/pedestal configurations, it has become conventional practice for the occupant restraint system used in trucks having pedestal mounted seats to comprise two principle components, namely, a seat belt apparatus and a seat tethering apparatus. The first component of the restraint system, the seat belt apparatus, ensures that the occupant remains positioned in the seat during a high acceleration event. The seat belt apparatus typically comprises conventional seat belt webbing and a latch mechanism, and may further comprise a shoulder belt and/or belt tensioning mechanisms, all of which are conventional and known in the art for restraining an occupant in a seat. Note, however, that the seat belt webbing and latch are not anchored to the floor of the vehicle, but rather are attached to a structural member, known in the industry as the interconnect point (hereafter xe2x80x9cICPxe2x80x9d), which is located on the lower rear portion of the seat or on the upper rear portion of the pedestal.
The second component of the occupant restraint system, the seat tethering apparatus, must restrain the seat against forward or upward movement relative to the floor of the vehicle during high acceleration events, a requirement which cannot generally be satisfied by the seat mounting pedestal alone. One commonly known seat tethering apparatus includes a pair of tether straps, each of which has one end connected to the ICP and another end connected to an anchor point located on the vehicle floor behind the seat. The tether straps are made of webbing material such as that used for seat belts. The tether straps may include mechanisms (one on each strap) to allow manual adjustment in length to accommodate vehicle-to-vehicle differences in the ICP-to-anchor distance and to accommodate adjustments in the static position of the seat relative to the vehicle floor. Proper use of the seat tethering apparatus requires the operator to manually adjust the length of each tether strap so that they are taut between the floor of the vehicle and the ICP on the base of the seat. In this manner, the forward and upward movement of the vehicle seat, and thus of an occupant properly belted into the seat, can be substantially limited relative to the floor of the vehicle during a collision. As a result, the occupant is less likely to incur substantial injuries by using the restraint system.
The conventional practice of using manually adjustable tether straps, however, does not necessarily ensure that the occupant will be optimally retrained in the event of a collision. Optimal restraint requires the length of each seat tether to be adjusted such that substantially all slack in the straps is eliminated. Ideally, the length of each tether strap would be adjusted to eliminate all slack each time the seat position is changed. Given human nature, however, many operators often fail to adjust the tether straps to eliminate the slack after each change in seat position, and further, some operators purposely adjust the tether straps with extra slack so that a full range of seat adjustment is possible at all times. Further, when the pedestal incorporates a suspension system, some slack must be intentionally left in the tether straps to accommodate the desirable movement of the seat through its range of suspension xe2x80x9ctravelxe2x80x9d due to the weight of the occupant and due to dynamic forces (e.g., bouncing) during normal operation of the vehicle. As a result of these factors, there typically will be some slack in conventional seat tethers during normal vehicle operation. This slack represents additional movement through which the occupant will travel during a collision before being restrained by the restraint system, and consequently an increased chance of injury. Therefore, a need exists for a seat tethering apparatus that automatically minimizes the slack in the seat tethers during normal vehicle operation, but without hindering the seat suspension functions and without being dependent on an operator""s diligence to tighten the tether straps.
Another concern regarding pedestal mounted vehicle seats relates to accidents in which a vehicle undergoes a rollover event. In such cases, the roof of the vehicle may be crushed inwards, thereby reducing the distance between the floor and the roof. Even though a conventional seat tethering apparatus can prevent the seat and occupant from moving toward the roof, it does nothing to protect the occupant from striking/being struck by the vehicle roof as it moves toward the floor. Therefore, a need exists for a seat tethering apparatus that increases the distance between the occupant""s head and the roof of the vehicle during a rollover event to reduce the chance of injury.
Many of the needs outlined above are addressed by the present invention hereof. It is an object of the present invention to provide a seat tethering apparatus that automatically minimizes the slack in the seat tethers during normal vehicle operation, but without hindering the seat suspension functions and without being dependent on an operator""s diligence to tighten the tether straps.
It is another object of the present invention to provide a seat tethering apparatus that increases the distance between the occupant""s head and the roof of the vehicle during a rollover event to reduce the chance of injury.
An apparatus for tethering a vehicle seat is provided that can be used for many vehicle applications, but which is particularly suited for use in the cabs of trucks, vans, and other large vehicles. The apparatus includes a webbing member, a sensing mechanism, and a retractor, wherein the retractor includes a spool assembly, a locking mechanism, and a biasing mechanism. The webbing member has one end attachable to a vehicle floor and a second end wound around the spool assembly of the retractor, wherein the retractor is attachable to a vehicle seat. The sensing mechanism senses at least two characteristics: a retractor operation characteristic and a vehicle collision characteristic. The sensing mechanism further produces a signal indicating which characteristic is currently being sensed. The locking mechanism of the retractor operates in response to the signal produced by the sensing mechanism. Specifically, the locking mechanism remains unlocked in response to the retractor operation characteristic and locks in response to the vehicle collision characteristic. The biasing mechanism of the retractor applies a constant force that urges the spool assembly in a direction that winds more of the webbing member toward the retractor. Accordingly, when the retractor operation characteristic is sensed, then the webbing member can be withdrawn from or retracted into the retractor depending on whether the tension applied to the webbing member is more or less than that applied by the biasing mechanism. Alternatively, when the vehicle collision characteristic is sensed, then the webbing member can be retracted further into the retractor if the tension applied is less than that applied by the biasing mechanism. The locking mechanism prevents the webbing member from being withdrawn further from the retractor.
In another embodiment, the webbing member includes an intermediate portion that passes through a corresponding guide portion, or webbing loop, attachable to a vehicle seat. In yet another embodiment, a retractor driving mechanism is included which applies a specified force to the webbing member in response to the vehicle collision signal produced by the sensing mechanism, thereby further retracting the webbing member into the retractor during a collision. In additional embodiments, various known types of drive sources can be used for the retractor driving mechanism, including a gas generator and a piston, a pneumatic piston, an air motor, an electric motor, and the like. In still further additional embodiments, various known types of sensors can be used for the sensing mechanism, including a centrifugal sensor, a pendulum sensor, an inertia sensor, a multi-axis sensor, an impact sensor, an electronic sensor, an accelerometer sensor, and the like.
In another embodiment, the apparatus for tethering a vehicle seat can include two or more webbing members, each of which is wound around the spool assembly of the retractor. In this embodiment, each of the webbing members includes an intermediate portion that passes through a corresponding guide portion, or webbing loop, attachable to a vehicle seat.
In another embodiment, the retractor can be attachable to an interior portion of a vehicle, and the webbing member can have a first end attachable to a vehicle seat and a second end wound around the spool assembly of the retractor.
In another embodiment, an apparatus is provided for effecting the method of retracting a vehicle seat when a vehicle is rolling over, including a vehicle seat, a sensor, and a retractor mechanism. In this embodiment, the sensor can at least sense whether a vehicle rollover is occurring and produce a signal when such a rollover begins. The retractor mechanism operates in response to this vehicle rollover signal and actively retracts the vehicle seat toward a floor of the vehicle. A further embodiment includes a vehicle seat, a retractor, a webbing member, a sensor mechanism, and a retractor driving mechanism. The retractor is attached to the base of the vehicle seat and includes a spool assembly. This embodiment also includes a webbing member with a first end attachable to the vehicle and a second end wound around the spool assembly of the retractor. The retractor driving mechanism causes the spool assembly to rotate in a direction that draws more of the webbing member into the retractor when a vehicle rollover signal is received from the sensor mechanism.